Long-Term Risk of Subsequent Neoplasms in 5-Year Survivors of Childhood Neuroblastoma: A Dutch Childhood Cancer Survivor Study-LATER 3 Study.

PURPOSE: Neuroblastoma survivors have an increased risk of developing subsequent malignant neoplasms (SMNs), but the risk of subsequent nonmalignant neoplasms (SNMNs) and risk factors are largely unknown. We analyzed the long-term risks and associated risk factors for developing SMNs and SNMNs in a well-characterized cohort of 5-year neuroblastoma survivors. METHODS: We included 563 5-year neuroblastoma survivors from the Dutch Childhood Cancer Survivor Study (DCCSS)-LATER cohort, diagnosed during 1963-2014. Subsequent neoplasms were ascertained by linkages with the Netherlands Cancer Registry and the Dutch Nationwide Pathology Databank (Palga) and medical chart review. We calculated standardized incidence ratios (SIRs), absolute excess risk (AER), and cumulative incidences. Multivariable competing risk regression analysis was used to evaluate risk factors. RESULTS: In total, 23 survivors developed an SMN and 60 an SNMN. After a median follow-up of 23.7 (range, 5.0-56.3) years, the risk of SMN was elevated compared with the general population (SIR, 4.0; 95% CI, 2.5 to 5.9; AER per 10,000 person-years, 15.1). The 30-year cumulative incidence was 3.4% (95% CI, 1.9 to 6.0) for SMNs and 10.4% (95% CI, 7.3 to 14.8) for SNMNs. Six survivors developed an SMN after iodine-metaiodobenzylguanidine (131IMIBG) treatment. Survivors treated with 131IMIBG had a higher risk of developing SMNs (subdistribution hazard ratio [SHR], 5.7; 95% CI, 1.8 to 17.8) and SNMNs (SHR, 2.6; 95% CI, 1.2 to 5.6) compared with survivors treated without 131IMIBG; results for SMNs were attenuated in high-risk patients only (SMNs SHR, 3.6; 95% CI, 0.9 to 15.3; SNMNs SHR, 1.5; 95% CI, 0.7 to 3.6). CONCLUSION: Our results demonstrate that neuroblastoma survivors have an elevated risk of developing SMNs and a high risk of SNMNs. 131IMIBG may be a treatment-related risk factor for the development of SMN and SNMN, which needs further validation. Our results emphasize the need for awareness of subsequent neoplasms and the importance of follow-up care.

Outcome after treatment with axitinib in children, young adults, and adults with renal cell carcinoma: a narrative review.

Renal cell carcinoma (RCC) is a very rare type of renal cancer in children and young adults. When metastasized or recurrent, no standards of care are available, and outcome is still poor. The tyrosine kinase inhibitor axitinib is approved for treatment of RCC in adults, but its effects in children and young adults with RCC remains unclear. Due to the histological and biological differences between children and adults, it is difficult to extrapolate knowledge on treatments from the adult to the pediatric and young adult setting. This paper summarizes the clinical characteristics and outcomes of patients with RCC who were treated with axitinib, with the aim to gain insight in the clinical efficacy of this compound in this young patient group.

A comprehensive overview of liquid biopsy applications in pediatric solid tumors.

Liquid biopsies are emerging as an alternative source for pediatric cancer biomarkers with potential applications during all stages of patient care, from diagnosis to long-term follow-up. While developments within this field are reported, these mainly focus on dedicated items such as a specific liquid biopsy matrix, analyte, and/or single tumor type. To the best of our knowledge, a comprehensive overview is lacking. Here, we review the current state of liquid biopsy research for the most common non-central nervous system pediatric solid tumors. These include neuroblastoma, renal tumors, germ cell tumors, osteosarcoma, Ewing sarcoma, rhabdomyosarcoma and other soft tissue sarcomas, and liver tumors. Within this selection, we discuss the most important or recent studies involving liquid biopsy-based biomarkers, anticipated clinical applications, and the current challenges for success. Furthermore, we provide an overview of liquid biopsy-based biomarker publication output for each tumor type based on a comprehensive literature search between 1989 and 2023. Per study identified, we list the relevant liquid biopsy-based biomarkers, matrices (e.g., peripheral blood, bone marrow, or cerebrospinal fluid), analytes (e.g., circulating cell-free and tumor DNA, microRNAs, and circulating tumor cells), methods (e.g., digital droplet PCR and next-generation sequencing), the involved pediatric patient cohort, and proposed applications. As such, we identified 344 unique publications. Taken together, while the liquid biopsy field in pediatric oncology is still behind adult oncology, potentially relevant publications have increased over the last decade. Importantly, steps towards clinical implementation are rapidly gaining ground, notably through validation of liquid biopsy-based biomarkers in pediatric clinical trials.

Targeted therapies in children with renal cell carcinoma (RCC): An International Society of Pediatric Oncology-Renal Tumor Study Group (SIOP-RTSG)-related retrospective descriptive study.

INTRODUCTION: Introduction: Renal cell carcinoma (RCC) is a very rare pediatric renal tumor. Robust evidence to guide treatment is lacking and knowledge on targeted therapies and immunotherapy is mainly based on adult studies. Currently, the International Society of Pediatric Oncology-Renal Tumor Study Group (SIOP-RTSG) 2016 UMBRELLA protocol recommends sunitinib for metastatic or unresectable RCC. METHODS: This retrospective study describes the effects of tyrosine kinase inhibitors (TKI), anti-programmed cell death 1 (PD-(L)1) monoclonal antibodies, and immunotherapeutic regimens in advanced-stage and relapsed pediatric RCC. RESULTS: Of the 31 identified patients (0-18 years) with histologically proven RCC, 3/31 presented with TNM stage I/II, 8/31 with TNM stage III, and 20/31 with TNM stage IV at diagnosis. The majority were diagnosed with translocation type RCC (MiT-RCC) (21/31) and the remaining patients mainly presented with papillary or clear-cell RCC. Treatment in a neoadjuvant or adjuvant setting, or upon relapse or progression, included mono- or combination therapy with a large variety of drugs, illustrating center specific choices in most patients. Sunitinib was often administered as first choice and predominantly resulted in stable disease (53%). Other frequently used drugs included axitinib, cabozantinib, sorafenib, and nivolumab; however, no treatment seemed more promising than sunitinib. Overall, 15/31 patients died of disease, 12/31 are alive with active disease, and only four patients had a complete response. The sample size and heterogeneity of this cohort only allowed descriptive statistical analysis. CONCLUSION: This study provides an overview of a unique series of clinical and treatment characteristics of pediatric patients with RCC treated with targeted therapies.

Integrative analysis of neuroblastoma by single-cell RNA sequencing identifies the NECTIN2-TIGIT axis as a target for immunotherapy.

Pediatric patients with high-risk neuroblastoma have poor survival rates and urgently need more effective treatment options with less side effects. Since novel and improved immunotherapies may fill this need, we dissect the immunoregulatory interactions in neuroblastoma by single-cell RNA-sequencing of 24 tumors (10 pre- and 14 post-chemotherapy, including 5 pairs) to identify strategies for optimizing immunotherapy efficacy. Neuroblastomas are infiltrated by natural killer (NK), T and B cells, and immunosuppressive myeloid populations. NK cells show reduced cytotoxicity and T cells have a dysfunctional profile. Interaction analysis reveals a vast immunoregulatory network and identifies NECTIN2-TIGIT as a crucial immune checkpoint. Combined blockade of TIGIT and PD-L1 significantly reduces neuroblastoma growth, with complete responses (CR) in vivo. Moreover, addition of TIGIT+PD-L1 blockade to standard relapse treatment in a chemotherapy-resistant Th-ALKF1174L/MYCN 129/SvJ syngeneic model induces CR. In conclusion, our integrative analysis provides promising targets and a rationale for immunotherapeutic combination strategies.

Targeted locus amplification to develop robust patient-specific assays for liquid biopsies in pediatric solid tumors.

Background: Liquid biopsies combine minimally invasive sample collection with sensitive detection of residual disease. Pediatric malignancies harbor tumor-driving copy number alterations or fusion genes, rather than recurrent point mutations. These regions contain tumor-specific DNA breakpoint sequences. We investigated the feasibility to use these breakpoints to design patient-specific markers to detect tumor-derived cell-free DNA (cfDNA) in plasma from patients with pediatric solid tumors. Materials and methods: Regions of interest (ROI) were identified through standard clinical diagnostic pipelines, using SNP array for CNAs, and FISH or RT-qPCR for fusion genes. Using targeted locus amplification (TLA) on tumor organoids grown from tumor material or targeted locus capture (TLC) on FFPE material, ROI-specific primers and probes were designed, which were used to design droplet digital PCR (ddPCR) assays. cfDNA from patient plasma at diagnosis and during therapy was analyzed. Results: TLA was performed on material from 2 rhabdomyosarcoma, 1 Ewing sarcoma and 3 neuroblastoma. FFPE-TLC was performed on 8 neuroblastoma tumors. For all patients, at least one patient-specific ddPCR was successfully designed and in all diagnostic plasma samples the patient-specific markers were detected. In the rhabdomyosarcoma and Ewing sarcoma patients, all samples after start of therapy were negative. In neuroblastoma patients, presence of patient-specific markers in cfDNA tracked tumor burden, decreasing during induction therapy, disappearing at complete remission and re-appearing at relapse. Conclusion: We demonstrate the feasibility to determine tumor-specific breakpoints using TLA/TLC in different pediatric solid tumors and use these for analysis of cfDNA from plasma. Considering the high prevalence of CNAs and fusion genes in pediatric solid tumors, this approach holds great promise and deserves further study in a larger cohort with standardized plasma sampling protocols.

Cell-Free RNA from Plasma in Patients with Neuroblastoma: Exploring the Technical and Clinical Potential.

Neuroblastoma affects mostly young children, bearing a high morbidity and mortality. Liquid biopsies, e.g., molecular analysis of circulating tumor-derived nucleic acids in blood, offer a minimally invasive diagnostic modality. Cell-free RNA (cfRNA) is released by all cells, especially cancer. It circulates in blood packed in extracellular vesicles (EV) or attached to proteins. We studied the feasibility of analyzing cfRNA and EV, isolated by size exclusion chromatography (SEC), from platelet-poor plasma from healthy controls (n = 40) and neuroblastoma patients with localized (n = 10) and metastatic disease (n = 30). The mRNA content was determined using several multiplex droplet digital PCR (ddPCR) assays for a neuroblastoma-specific gene panel (PHOX2B, TH, CHRNA3) and a cell cycle regulation panel (E2F1, CDC6, ATAD2, H2AFZ, MCM2, DHFR). We applied corrections for the presence of platelets. We demonstrated that neuroblastoma-specific markers were present in plasma from 14/30 patients with metastatic disease and not in healthy controls and patients with localized disease. Most cell cycle markers had a higher expression in patients. The mRNA markers were mostly present in the EV-enriched SEC fractions. In conclusion, cfRNA can be isolated from plasma and EV and analyzed using multiplex ddPCR. cfRNA is an interesting novel liquid biopsy-based target to explore further.

Optimising urinary catecholamine metabolite diagnostics for neuroblastoma.

INTRODUCTION: The analysis of urinary catecholamine metabolites is a cornerstone of neuroblastoma diagnostics. Currently, there is no consensus regarding the sampling method, and variable combinations of catecholamine metabolites are being used. We investigated if spot urine samples can be reliably used for analysis of a panel of catecholamine metabolites for the diagnosis of neuroblastoma. METHODS: Twenty-four-hour urine or spot urine samples were collected from patients with and without neuroblastoma at diagnosis. Homovanillic acid (HVA), vanillylmandelic acid (VMA), dopamine, 3-methoxytyramine, norepinephrine, normetanephrine, epinephrine and metanephrine were measured by high-performance liquid chromatography coupled with fluorescence detection (HPLC-FD) and/or ultra-performance liquid chromatography coupled with electrospray tandem mass spectrometry (UPLC-MS/MS). RESULTS: Catecholamine metabolite levels were measured in urine samples of 400 neuroblastoma patients (24-hour urine, n = 234; spot urine, n = 166) and 571 controls (all spot urine). Excretion levels of catecholamine metabolites and the diagnostic sensitivity for each metabolite were similar in 24-hour urine and spot urine samples (p > .08 and >.27 for all metabolites). The area under the receiver-operating-characteristic curve (AUC) of the panel containing all eight catecholamine metabolites was significantly higher compared to that of only HVA and VMA (AUC = 0.952 vs. 0.920, p = .02). No differences were observed in metabolite levels between the two analysis methods. CONCLUSION: Catecholamine metabolites in spot urine and 24-hour urine resulted in similar diagnostic sensitivities. The Catecholamine Working Group recommends the implementation of spot urine as standard of care. The panel of eight catecholamine metabolites has superior diagnostic accuracy over VMA and HVA.

MEK inhibition causes BIM stabilization and increased sensitivity to BCL-2 family member inhibitors in RAS-MAPK-mutated neuroblastoma.

Introduction: Mutations affecting the RAS-MAPK pathway occur frequently in relapsed neuroblastoma tumors and are associated with response to MEK inhibition in vitro. However, these inhibitors alone do not lead to tumor regression in vivo, indicating the need for combination therapy. Methods and results: Via high-throughput combination screening, we identified that the MEK inhibitor trametinib can be combined with BCL-2 family member inhibitors, to efficiently inhibit growth of neuroblastoma cell lines with RAS-MAPK mutations. Suppressing the RAS-MAPK pathway with trametinib led to an increase in pro-apoptotic BIM, resulting in more BIM binding to anti-apoptotic BCL-2 family members. By favoring the formation of these complexes, trametinib treatment enhances sensitivity to compounds targeting anti-apoptotic BCL-2 family members. In vitro validation studies confirmed that this sensitizing effect is dependent on an active RAS-MAPK pathway. In vivo combination of trametinib with BCL-2 inhibitors led to tumor inhibition in NRAS-mutant and NF1-deleted xenografts. Conclusion: Together, these results show that combining MEK inhibition with BCL-2 family member inhibition could potentially improve therapeutic outcomes for RAS-MAPK-mutated neuroblastoma patients.

Humanized MISTRG as a preclinical in vivo model to study human neutrophil-mediated immune processes.

Introduction: MISTRG mice have been genetically modified to allow development of a human myeloid compartment from engrafted human CD34+ haemopoietic stem cells, making them particularly suited to study the human innate immune system in vivo. Here, we characterized the human neutrophil population in these mice to establish a model that can be used to study the biology and contribution in immune processes of these cells in vivo. Methods and results: We could isolate human bone marrow neutrophils from humanized MISTRG mice and confirmed that all neutrophil maturation stages from promyelocytes (CD11b-CD16-) to end-stage segmented cells (CD11b+CD16+) were present. We documented that these cells possessed normal functional properties, including degranulation, reactive oxygen species production, adhesion, and antibody-dependent cellular cytotoxicity towards antibody-opsonized tumor cells ex vivo. The acquisition of functional capacities positively correlated with the maturation state of the cell. We found that human neutrophils were retained in the bone marrow of humanized MISTRG mice during steady state. However, the mature segmented CD11b+CD16+ human neutrophils were released from the bone marrow in response to two well-established neutrophil-mobilizing agents (i.e., G-CSF and/or CXCR4 antagonist Plerixafor). Moreover, the neutrophil population in the humanized MISTRG mice actively reacted to thioglycolate-induced peritonitis and could infiltrate implanted human tumors, as shown by flow cytometry and fluorescent microscopy. Discussion: These results show that functional human neutrophils are generated and can be studied in vivo using the humanized MISTRG mice, providing a model to study the various functions of neutrophils in inflammation and in tumors.

Cell-Free DNA as a Diagnostic and Prognostic Biomarker in Pediatric Rhabdomyosarcoma.

PURPOSE: Total cell-free DNA (cfDNA) and tumor-derived cfDNA (ctDNA) can be used to study tumor-derived genetic aberrations. We analyzed the diagnostic and prognostic potential of cfDNA and ctDNA, obtained from pediatric patients with rhabdomyosarcoma. METHODS: cfDNA was isolated from diagnostic plasma samples from 57 patients enrolled in the EpSSG RMS2005 study. To study the diagnostic potential, shallow whole genome sequencing (shWGS) and cell-free reduced representation bisulphite sequencing (cfRRBS) were performed in a subset of samples and all samples were tested using droplet digital polymerase chain reaction to detect methylated RASSF1A (RASSF1A-M). Correlation with outcome was studied by combining cfDNA RASSF1A-M detection with analysis of our rhabdomyosarcoma-specific RNA panel in paired cellular blood and bone marrow fractions and survival analysis in 56 patients. RESULTS: At diagnosis, ctDNA was detected in 16 of 30 and 24 of 26 patients using shallow whole genome sequencing and cfRRBS, respectively. Furthermore, 21 of 25 samples were correctly classified as embryonal by cfRRBS. RASSF1A-M was detected in 21 of 57 patients. The presence of RASSF1A-M was significantly correlated with poor outcome (the 5-year event-free survival [EFS] rate was 46.2% for 21 RASSF1A-M‒positive patients, compared with 84.9% for 36 RASSF1A-M‒negative patients [P < .001]). RASSF1A-M positivity had the highest prognostic effect among patients with metastatic disease. Patients both negative for RASSF1A-M and the rhabdomyosarcoma-specific RNA panel (28 of 56 patients) had excellent outcome (5-year EFS 92.9%), while double-positive patients (11/56) had poor outcome (5-year EFS 13.6%, P < .001). CONCLUSION: Analyzing ctDNA at diagnosis using various techniques is feasible in pediatric rhabdomyosarcoma and has potential for clinical use. Measuring RASSF1A-M in plasma at initial diagnosis correlated significantly with outcome, particularly when combined with paired analysis of blood and bone marrow using a rhabdomyosarcoma-specific RNA panel.

[18F]mFBG PET-CT for detection and localisation of neuroblastoma: a prospective pilot study.

PURPOSE: Meta-[18F]fluorobenzylguanidine ([18F]mFBG) is a positron emission tomography (PET) radiotracer that allows for fast and high-resolution imaging of tumours expressing the norepinephrine transporter. This pilot study investigates the feasibility of [18F]mFBG PET-CT for imaging in neuroblastoma. METHODS: In a prospective, single-centre study, we recruited children with neuroblastoma, referred for meta-[123I]iodobenzylguanidine ([123I]mIBG) scanning, consisting of total body planar scintigraphy in combination with single-photon emission computed tomography-CT (SPECT-CT). Within two weeks of [123I]mIBG scanning, total body PET-CTs were performed at 1 h and 2 h after injection of [18F]mFBG (2 MBq/kg). Detected tumour localisations on scan pairs were compared. Soft tissue disease was quantified by number of lesions and skeletal disease by SIOPEN score. RESULTS: Twenty paired [123I]mIBG and [18F]mFBG scans were performed in 14 patients (median age 4.9 years, n = 13 stage 4 disease and n = 1 stage 4S). [18F]mFBG injection was well tolerated and no related adverse events occurred in any of the patients. Mean scan time for [18F]mFBG PET-CT (9.0 min, SD 1.9) was significantly shorter than for [123I]mIBG scanning (84.5 min, SD 10.5), p < 0.01. Most tumour localisations were detected on the 1 h versus 2 h post-injection [18F]mFBG PET-CT. Compared to [123I]mIBG scanning, [18F]mFBG PET-CT detected a higher, equal, and lower number of soft tissue lesions in 40%, 55%, and 5% of scan pairs, respectively, and a higher, equal, and lower SIOPEN score in 55%, 30%, and 15% of scan pairs, respectively. On average, two more soft tissue lesions and a 6-point higher SIOPEN score were detected per patient on [18F]mFBG PET-CT compared to [123I]mIBG scanning. CONCLUSION: Results of this study demonstrate feasibility of [18F]mFBG PET-CT for neuroblastoma imaging. More neuroblastoma localisations were detected on [18F]mFBG PET-CT compared to [123I]mIBG scanning. [18F]mFBG PET-CT shows promise for future staging and response assessment in neuroblastoma. TRIAL REGISTRATION: Dutch Trial Register NL8152.

Molecular Characterization of Circulating Tumor DNA in Pediatric Rhabdomyosarcoma: A Feasibility Study.

PURPOSE: Rhabdomyosarcomas (RMS) are rare neoplasms affecting children and young adults. Efforts to improve patient survival have been undermined by a lack of suitable disease markers. Plasma circulating tumor DNA (ctDNA) has shown promise as a potential minimally invasive biomarker and monitoring tool in other cancers; however, it remains underexplored in RMS. We aimed to determine the feasibility of identifying and quantifying ctDNA in plasma as a marker of disease burden and/or treatment response using blood samples from RMS mouse models and patients. METHODS: We established mouse models of RMS and applied quantitative polymerase chain reaction (PCR) and droplet digital PCR (ddPCR) to detect ctDNA within the mouse plasma. Potential driver mutations, copy-number alterations, and DNA breakpoints associated with PAX3/7-FOXO1 gene fusions were identified in the RMS samples collected at diagnosis. Patient-matched plasma samples collected from 28 patients with RMS before, during, and after treatment were analyzed for the presence of ctDNA via ddPCR, panel sequencing, and/or whole-exome sequencing. RESULTS: Human tumor-derived DNA was detectable in plasma samples from mouse models of RMS and correlated with tumor burden. In patients, ctDNA was detected in 14/18 pretreatment plasma samples with ddPCR and 7/7 cases assessed by sequencing. Levels of ctDNA at diagnosis were significantly higher in patients with unfavorable tumor sites, positive nodal status, and metastasis. In patients with serial plasma samples (n = 18), fluctuations in ctDNA levels corresponded to treatment response. CONCLUSION: Comprehensive ctDNA analysis combining high sensitivity and throughput can identify key molecular drivers in RMS models and patients, suggesting potential as a minimally invasive biomarker. Preclinical assessment of treatments using mouse models and further patient testing through prospective clinical trials are now warranted.

Chromosome 11q loss and MYCN amplification demonstrate synthetic lethality with checkpoint kinase 1 inhibition in neuroblastoma.

Neuroblastoma is the most common extracranial solid tumor found in children and despite intense multi-modal therapeutic approaches, low overall survival rates of high-risk patients persist. Tumors with heterozygous loss of chromosome 11q and MYCN amplification are two genetically distinct subsets of neuroblastoma that are associated with poor patient outcome. Using an isogenic 11q deleted model system and high-throughput drug screening, we identify checkpoint kinase 1 (CHK1) as a potential therapeutic target for 11q deleted neuroblastoma. Further investigation reveals MYCN amplification as a possible additional biomarker for CHK1 inhibition, independent of 11q loss. Overall, our study highlights the potential power of studying chromosomal aberrations to guide preclinical development of novel drug targets and combinations. Additionally, our study builds on the growing evidence that DNA damage repair and replication stress response pathways offer therapeutic vulnerabilities for the treatment of neuroblastoma.

Incidence and survival of paediatric renal tumours in the Netherlands between 1990 and 2014.

BACKGROUND: This population-based study is the first to provide a detailed analysis of trends in incidence and survival of children and adolescents diagnosed with renal malignancies in the Netherlands. METHODS: Data on all renal malignancies diagnosed in paediatric patients (0-18 years) between 1990 and 2014 [N = 648, 92% Wilms tumour (WT)] were extracted from the Netherlands Cancer Registry. Five-year overall survival (OS) was estimated using the actuarial method. Time trends in incidence were assessed by calculating average annual percentage change. A parametric survival model was used to compare the multivariable-adjusted risk of dying from WT between two diagnostic periods. RESULTS: The incidence was 8 per million person-years and was constant over time (average annual percentage change -0.8%, p = 0.29). Patients with WT had a favourable outcome in both time periods; 5-year OS was 88% in 1990-2001 and 91% in 2002-2014. Multivariable analysis showed that the risk of dying from WT was not significantly decreased in the latest period (hazard ratio, 95% CI: 0.7, 0.4-1.3). Five-year OS decreased with increasing disease stage, ranging from 95 to 100% for stage I-II and about 80% for stage III-IV to 74% for bilateral disease. Five-year OS were 81% for renal cell carcinoma, 77% for clear cell sarcoma of the kidney and 20% for malignant rhabdoid tumour of the kidney. CONCLUSIONS: Incidence of paediatric renal malignancies in the Netherlands has been stable since the 1990s. Five-year OS of WT reached 91% and was similar to findings for other developed countries. Contrary to the excellent outcome for WT, the outcome of malignant rhabdoid tumour of the kidney remained inferior.

Extracellular Vesicles: A New Source of Biomarkers in Pediatric Solid Tumors? A Systematic Review.

Virtually every cell in the body releases extracellular vesicles (EVs), the contents of which can provide a "fingerprint" of their cellular origin. EVs are present in all bodily fluids and can be obtained using minimally invasive techniques. Thus, EVs can provide a promising source of diagnostic, prognostic, and predictive biomarkers, particularly in the context of cancer. Despite advances using EVs as biomarkers in adult cancers, little is known regarding their use in pediatric cancers. In this review, we provide an overview of published clinical and in vitro studies in order to assess the potential of using EV-derived biomarkers in pediatric solid tumors. We performed a systematic literature search, which yielded studies regarding desmoplastic small round cell tumor, hepatoblastoma, neuroblastoma, osteosarcoma, and rhabdomyosarcoma. We then determined the extent to which the in vivo findings are supported by in vitro data, and vice versa. We also critically evaluated the clinical studies using the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) system, and we evaluated the purification and characterization of EVs in both the in vivo and in vitro studies in accordance with MISEV guidelines, yielding EV-TRACK and PedEV scores. We found that several studies identified similar miRNAs in overlapping and distinct tumor entities, indicating the potential for EV-derived biomarkers. However, most studies regarding EV-based biomarkers in pediatric solid tumors lack a standardized system of reporting their EV purification and characterization methods, as well as validation in an independent cohort, which are needed in order to bring EV-based biomarkers to the clinic.

Thyroid function after diagnostic 123I-metaiodobenzylguanidine in children with neuroblastic tumors.

BACKGROUND: Metaiodobenzylguanidine (MIBG) labeled with radioisotopes can be used for diagnostics 123I-) and treatment (131I-) in patients with neuroblastic tumors. Thyroid dysfunction has been reported in 52% of neuroblastoma (NBL) survivors after 131I-MIBG, despite thyroid protection. Diagnostic 123I-MIBG is not considered to be hazardous for thyroid function; however, this has never been investigated. Therefore, the aim of this study was to evaluate the prevalence of thyroid dysfunction in survivors of a neuroblastic tumor who received diagnostic 123I-MIBG only. METHODS: Thyroid function and uptake of 123I- in the thyroid gland after 123I-MIBG administrations were evaluated in 48 neuroblastic tumor survivors who had not been treated with 131I-MIBG. All patients had received thyroid prophylaxis consisting of potassium iodide or a combination of potassium iodide, thiamazole and thyroxine during exposure to 123I-MIBG. RESULTS: After a median follow-up of 6.6 years, thyroid function was normal in 46 of 48 survivors (95.8%). Two survivors [prevalence 4.2% (95% CI 1.2-14.0)] had mild thyroid dysfunction. In 29.2% of the patients and 11.1% of images 123I- uptake was visible in the thyroid. In 1 patient with thyroid dysfunction, weak uptake of 123I- was seen on 1 of 10 images. CONCLUSIONS: The prevalence of thyroid dysfunction does not seem to be increased in patients with neuroblastic tumors who received 123I-MIBG combined with thyroid protection. Randomized controlled trials are required to investigate whether administration of 123I-MIBG without thyroid protection is harmful to the thyroid gland.

Mutational spectrum of ATRX aberrations in neuroblastoma and associated patient and tumor characteristics.

Neuroblastoma is the most common extracranial solid tumor in children. The chromatin remodeler ATRX is frequently mutated in high-risk patients with a poor prognosis. Although many studies have reported ATRX aberrations and the associated clinical characteristics in neuroblastoma, a comprehensive overview is currently lacking. In this study, we extensively characterize the mutational spectrum of ATRX aberrations in neuroblastoma tumors reported in previous studies and present an overview of patient and tumor characteristics. We collected the data of a total of 127 neuroblastoma patients and three cell lines with ATRX aberrations originating from 20 papers. We subdivide the ATRX aberrations into nonsense, missense, and multiexon deletions (MEDs) and show that 68% of them are MEDs. Of these MEDs, 75% are predicted to be in-frame. Furthermore, we identify a missense mutational hotspot region in the helicase domain. We also confirm that all three ATRX mutation types are more often identified in patients diagnosed at an older age, but still approximately 40% of the patients are aged 5 years or younger at diagnosis. Surprisingly, we found that 11q deletions are enriched in neuroblastomas with ATRX deletions compared to a reference cohort, but not in neuroblastomas with ATRX point mutations. Taken together, our data emphasizes a distinct ATRX mutation spectrum in neuroblastoma, which should be considered when studying molecular phenotypes and therapeutic strategies.